     (re-frame/reg-sub
      :before-locations-count
      :<- [:partitioned-locations]
-     (fn [[before _ _] _]
+     (fn before-locations-count [[before _ _] _]
        (count before)))
 
     (re-frame/reg-sub
      :after-locations-count
      :<- [:partitioned-locations]
-     (fn [[_ _ after] _]
+     (fn after-locations-count [[_ _ after] _]
        (count after)))
 
     (re-frame/reg-sub

     :current-locations
     :<- [:partitioned-locations]
     :<- [:buffer-size]
     (fn [[partitioned-locations buffer-size] _]
       (current-locations partitioned-locations buffer-size)))))

(defn- location-id [location]


(defn setup! []
  (trace-forms {:tracer (tracer :color "green")}
    (re-frame/reg-event-db
     :set-current-location
     (fn set-current-version-event [app-db [_ current-location]]
       (assoc app-db :current-location current-location)))

    (re-frame/reg-event-db
     :add-locations
     (fn add-locations-event [app-db [_ locations]]
       (add-locations app-db locations)))

    (re-frame/reg-event-db
     :set-buffer-size
     (fn set-buffer-size-event [app-db [_ n]]
       (assoc app-db :buffer-size n))))

  (trace-forms {:tracer (tracer :color "brown")}
    (re-frame/reg-sub
     :locations
     (fn locations [app-db _]
       (:locations app-db)))

    (re-frame/reg-sub
     :current-location
     (fn current-location [app-db _]
       (:current-location app-db)))

    (re-frame/reg-sub
     :buffer-size
     (fn buffer-size [app-db _]
       (:buffer-size app-db)))

    ;; Level two subscription

